Efforts have been made to position propulsion units at the sterns of multihull vessels, such as catamarans and trimarans.
For lightweight hulls, such as those employed in beach catamarans, however, there is inadequate floatation and height above the waterline at this location to protect the propulsion unit from splashing or immersion, particularly if the operator is near the back of the boat. Additionally, excess weight at the back of the boat tends to immerse the transoms when underway, which produces much drag for a displacement hull. A technique for protecting the propulsion units from water would be desirable, as well as a technique powering a lightweight powered catamaran that makes headway without immersing the transoms.
A further consideration relating to positioning the propulsion units at the stern is the necessity of positioning the props deeply enough in the water so that they do not come out of the water during ordinary wave action, cavitate, or aspirate. A technique for running the propulsion units very shallow, which would reduce drag, and thus increase speed and efficiency, and reduce the possibility of striking an underwater object, and further not lose efficiency by coming out of the water, cavitating, or aspirating, would be very desirable.
An additional consideration with stern mounted propulsion units is the provision of the steering mechanism, which presents a tripping hazard and attack point for corrosion, power sources, such as batteries or fuel tanks, which affect the trim of the vessel and present a tripping hazard, and lines such as fuel lines and/or battery cables, running from the power sources to the propulsion units, which present a tripping hazard, and in the case of battery cables, waste energy. A technique which minimizes tripping hazards, does not affect vessel trim, and keeps fuel lines, control lines, and battery cables short, would be very desirable.
A power boat capable of being launched from the beach would be very desirable.
A boat capable of running on solar-electric power would be very desirable.